Fluid treatment system and process

ABSTRACT

A fluid treatment system and process includes structure and steps relating to a gravity fed fluid treatment system. A fluid inlet and a fluid outlet are provided, and an irradiation zone is disposed between the fluid inlet and the fluid outlet. The irradiation zone includes at least one radiation source and has a closed cross-section to confine fluid to be treated within a predefined maximum distance from the at least one radiation source. Cleaning structure is provided to remove undesired materials from an exterior of the radiation source. The cleaning structure comprises a cleaning sleeve surrounding the radiation source and movable with respect thereto. The cleaning solution includes a chamber surrounding and in contact with the exterior of the radiation source, the chamber being supplied with a cleaning solution suitable to remove undesired materials from the exterior of the radiation source.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of treating fluid by providinga gravity fed flow of fluid to an irradiation zone comprising at leastone radiation source and having a closed cross-section which confinesthe flow of fluid within a predefined maximum distance from the at leastone radiation source.

The present invention also relates to a novel method of cleaning aradiation source assembly located within a fluid flow wherein theexterior of the source is swept by a cleaning member containing anappropriate cleaning solution.

The present invention also relates to a novel system for treating fluidby exposing it to radiation. Specifically, the present invention relatesto a novel gravity fed system for treating fluids comprising a treatmentzone which includes a irradiation zone configured to provide a fixedfluid geometry relative to the radiation sources.

The present invention also relates to a novel radiation source modulefor use in a fluid treatment system. Specifically, the module includesone or more radiation source assemblies connected to a support memberand the support member is designed to permit insertion and extraction ofthe module from the treatment system while the system is in use. Themodule is designed such that the radiation source assembly is preventedfrom contacting surfaces within the treatment zone of the system whilebeing installed or removed.

The present invention also relates to a novel cleaning apparatus forfluid treatment systems. Specifically, the cleaning apparatus includesone or more cleaning members which may be swept over the exterior ofradiation source assemblies within the fluid treatment system, thecleaning members containing a suitable cleaning fluid which contacts theexterior of the radiation source assembly and loosens and/or removesmaterials fouling the exterior of the radiation source assembly.

2. Description of the Prior Art

Fluid treatment systems are known. For example, U.S. Pat. Nos.4,482,809, 4,872,980 and 5,006,244 (assigned to the assignee of thepresent invention), the contents of each of which are herebyincorporated by reference, all describe gravity fed fluid treatmentsystems which employ ultraviolet (UV) radiation.

Such systems include an array of UV lamp frames which include several UVlamps each of which are mounted within sleeves extending between twosupport arms of the frames. The flames are immersed into the fluid to betreated which is then irradiated as required. The amount of radiation towhich the fluid is exposed is determined by the proximity of the fluidto the lamps, the output wattage of the lamps and the fluid's flow ratepast the lamps. One or more UV sensors may be employed to monitor the UVoutput of the lamps and the fluid level is typically controlled, to someextent, downstream of the treatment device by means of level gates orthe like. Since accurate fluid level control is difficult to achieve ingravity fed systems, fluctuations in fluid level are inevitable. Suchfluctuations could lead to non-uniform irradiation in the treated fluid.

However, disadvantages exist with the above-described systems. Dependingupon the quality of the fluid which is being treated, the sleevessurrounding the UV lamps periodically become fouled with foreignmaterials, inhibiting their ability to transmit UV radiation to thefluid. When fouled, at intervals which may be determined from historicaloperating data or by the measurements from the UV sensors, the sleevesmust be manually cleaned to remove the fouling materials.

If the UV lamp frames are employed in an open, channel-like system, oneor more of the flames may be removed while the system continues tooperate, and the removed frames may be immersed in a bath of suitableacidic cleaning solution which is air-agitated to remove foulingmaterials. Of course, surplus or redundant sources of UV radiation mustbe provided (usually by including extra UV lamp frames) to ensureadequate irradiation of the fluid being treated while one or more of theframes has been removed for cleaning. Of course, this required surplusUV capacity adds to the expense of installing the treatment system.

Further, a cleaning vessel containing cleaning solution into which UVlamp frames may be placed must also be provided and maintained.Depending upon the number of frames to be cleaned at one time and thefrequency at which they require cleaning, this can also significantlyadd to the expense of installing, maintaining and operating thetreatment system.

If the frames are in a closed system, removal of the frames from thefluid for cleaning is usually impractical. In this case, the sleevesmust be cleaned by suspending treatment of the fluid, shutting inlet andoutlet valves to the treatment enclosure and filling the entiretreatment enclosure with the acidic cleaning solution and air-agitatingthe fluid to remove the fouling materials. Cleaning such closed systemssuffers from the disadvantages that the treatment system must be stoppedwhile cleaning proceeds and that a large quantity of cleaning solutionmust be employed to fill the treatment enclosure. An additional problemexists in that handling large quantities of acidic cleaning fluid ishazardous and disposing of large quantities of used cleaning fluid isdifficult and/or expensive. Of course open flow systems suffer fromthese two problems, albeit to a lesser degree.

Indeed, it is the belief of the present inventor that, once installed,one of the largest costs associated with prior art fluid treatmentsystems is often the cost of cleaning of the sleeves about the radiationsources.

Another disadvantage with the above-described prior art systems is theoutput of the UV lamps. Unfortunately, the UV lamps in the prior artsystems were required to be about five feet in length to provide thenecessary wattage of UV radiation. Accordingly, the UV lamps wererelatively fragile and required support at each end of the lamp. Thisincreased the capital cost of the system.

Further, due to the somewhat limited output wattage of the UV lamps inthe prior art systems, a great number of lamps were often required. Forexample, certain prior art installations employ over 9,000 lamps. Such ahigh number of lamps adds to the above-mentioned costs in cleaning lampsas well as the cost of maintaining (replacing) the lamps.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel method oftreating a fluid by irradiation which obviates or mitigates at least oneof the above-mentioned disadvantages of the prior art.

It is a further object of the present invention to provide a novel fluidtreatment system which obviates or mitigates at least one of theabove-mentioned disadvantages of the prior art.

According to one aspect of the present invention, there is provided amethod of treating a fluid comprising the steps of:

(i) providing a gravity fed flow of fluid to a fluid inlet;

(ii) feeding the flow of fluid from the fluid inlet to an irradiationzone comprising at least one radiation source and having a closedcross-section;

(iii) confining the flow of fluid within a predefined maximum distancefrom the at least one radiation source;

(iv) exposing the flow of fluid to radiation from the radiation source;and

(v) feeding the flow of fluid from step (iv) to a fluid outlet.

According to another aspect of the present invention, there is provideda method of removal of fouling materials from a radiation source in situin a fluid treatment system, comprising the steps of:

(i) providing a supply of a cleaning fluid to a cleaning chamber;

(ii) moving the cleaning chamber into contact with at least a portion ofthe radiation source for a predetermined time period, the cleaningchamber maintaining the cleaning fluid in contact with the portion; and

(iii) removing the cleaning chamber from contact with the portion of theradiation source after the predetermined time period.

According to another aspect of the present invention, there is provideda gravity fed fluid treatment system comprising a fluid inlet, a fluidoutlet, and an irradiation zone disposed between the fluid inlet andfluid outlet, the irradiation zone (i) including at least one radiationsource and, (ii) having a closed cross-section to confine fluid to betreated within a predefined maximum distance from the at least oneradiation source assembly.

Preferably, the irradiation zone is disposed within a fluid treatmentzone including an inlet transition region and an outlet transitionregion. The inlet transition region receives the fluid flow from thefluid inlet and increases its velocity prior to entry thereof into theirradiation zone. The outlet transition region receives the fluid flowfrom the irradiation zone and decreases the velocity of the fluid flowprior to its entry into the fluid outlet. Thus, the fluid flow velocityis only elevated within the irradiation zone to reduce hydraulic headloss of the fluid flow through the system.

According to another aspect of the present invention, there is provideda radiation source module for use in a fluid treatment systemcomprising: a support member; at least one radiation source assemblyextending from said support member; and a guide and support memberextending from said support member; wherein said at least one radiationsource assembly extends from said support member substantially parallelto said guide and support member, said guide and support memberextending from said support member and having a free end.

According to yet another aspect of the present invention, there isprovided a cleaning apparatus for a radiation source assembly in a fluidtreatment system, comprising: a cleaning sleeve engaging a portion ofthe exterior said radiation source assembly and movable between aretracted position wherein a first portion of said radiation source isexposed to a flow of fluid to be treated and an extended positionwherein said first portion of said radiation source assembly is coveredby said cleaning sleeve, said cleaning sleeve including a chamber incontact with said first portion of said radiation source assembly andbeing supplied with a cleaning solution suitable to remove undesiredmaterials from said first portion.

According to another aspect of the invention, there is provided aradiation sensor assembly comprising: a sensor housing; a radiationtransmissive means within said housing and including a portion to beexposed to a radiation source; a radiation sensor receiving radiationfrom said transmissive means; and means to remove materials fouling saidportion.

As used herein, the term "gravity fed" encompasses systems wherein thehydraulic head of the fluid is obtained from changes in the altitude ofthe fluid. It will be understood that such systems comprise both systemswhich are naturally gravity fed and systems wherein the altitude of thefluid is altered via pumps or other mechanical means to provide agravity feed.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described with reference tothe accompanying drawings, in which:

FIG. 1 illustrates a side section of a prior art fluid treatment device;

FIG. 2 illustrates an end section of the prior art fluid treatmentdevice of FIG. 1;

FIG. 3 illustrates a side section of a first embodiment of a horizontalfluid treatment system in accordance with the present invention;

FIG. 4 illustrates a radiation source module for use with the system ofFIG. 3;

FIG. 5 illustrates an expanded view of the area indicated at A in FIG.4;

FIG. 6 illustrates a portion of another embodiment of a radiation sourcemodule for use with the system of FIG. 3;

FIG. 7 illustrates an expanded view of the area indicated at B in FIG.6;

FIG. 8 illustrates a side section of a second embodiment of a verticalfluid treatment system in accordance with the present invention; and

FIG. 9 illustrates a radiation sensor assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For clarity, a brief description of a prior art fluid treatment devicewill be presented before discussing the present invention. FIGS. 1 and 2show a prior art treatment device as described in U.S. Pat. No.4,482,809. The device includes a plurality of radiation source modules20, each including a pair of frame legs 24 with UV lamp assemblies 28extending therebetween. As best shown in FIG. 2, a plurality of lampmodules 20 are arranged across a treatment canal 32 with a maximumspacing between lamp modules 20 which is designed to ensure that thefluid to be treated is irradiated with at least a predetermined minimumdosage of UV radiation.

While this system has been successful, as discussed above it suffersfrom disadvantages in that the arrangement of the lamp modules 20 makesmaintenance of the device relatively labour intensive. Specifically,replacing lamps or cleaning the sleeves surrounding the lamps is timeconsuming and expensive. Also, for treatment to continue when a lampmodule is removed, it is necessary to provide redundant lamp modules toensure that the fluid still receives the predefined minimum dosage ofradiation increasing the cost of the system. Further, depending on thequality of the fluid and its flow rate, significant numbers of lamps andsleeves may be required per unit of fluid treated. Another disadvantageof this prior art system is the difficulty in controlling fluid levelrelative to lamp modules 20 at various flow rates.

Accordingly, while the above-described prior art systems have beensuccessful, the present inventor has been concerned with improving fluidtreatment systems to overcome some of these disadvantages. The presentinvention will now be described with reference to the remaining Figures.

Referring now to FIG. 3, a fluid treatment system in accordance with thepresent invention is indicated generally at 100. The system 100 includesa main body 104 which is installed across an open fluid canal 108 suchthat the all of the fluid flow through canal 108 is directed through atreatment zone 112. Main body 104 may be precast concrete, stainlesssteel or any other material suitable for use with the fluid to betreated and which is resistant to the type of radiation employed.

The lower surface of main body 104 includes a central section 116 whichextends downward with leading and trailing inclined sections 120 and124, respectively. A corresponding upraised central section 132 islocated on the base 128 of canal 108 beneath central section 116 andincludes leading and trailing inclined sections 136 and 140,respectively. Central section 132 may be part of main body 104 or may bepart of base 128 (as illustrated).

As can be clearly seen in FIG. 3, sections 116 and 132 form a narrowedirradiation zone 144, while sections 120 and 136 form a tapered inlettransition region and sections 124 and 140 form a tapered outlettransition region.

As will be apparent, irradiation zone 144 presents a closedcross-section to the fluid to be treated. This provides a fixed geometryof the fluid relative to irradiation sources (described hereinafter) toensure that the fluid is exposed to the predefined minimum radiationfrom the irradiation sources.

At least one of the upstream and downstream faces of main body 104includes one or more radiation source modules 148 mounted thereto.Depending on the fluid to be treated, the number of modules 148 providedmay be varied from a single upstream module 148 to two or more modules148 across both the upstream and downstream faces of main body 104. Whenupstream and downstream modules 148 are provided, the modules 148 arestaggered horizontally as will be further described when modules 148 arediscussed in more detail hereinbelow.

Main body 104 also includes a radiation sensor 152 which extends intoirradiation zone 144 and a fluid level sensor 156 which monitors thelevel of fluid in the inlet side of treatment zone 112. As is known tothose of skill in the art, if the level of fluid in the system fallsbelow fluid level sensor 156, an alarm or shutdown of the radiationsources will occur, as appropriate. A standard fluid levelling gate 150is also provided downstream of main body 104 to maintain a minimum fluidlevel in treatment zone 112.

As best shown in FIGS. 4 and 5, each radiation source module 148includes a radiation source support leg 160, a horizontal support andguide member 164, a connector box 172 and one or more radiation sourceassemblies 176 adjacent the lower extremity of support leg 160. Eachradiation source assembly 176 includes a high intensity radiation source180 such as a HOK35-80 Ultraviolet lamp made by Philips which is mountedwithin a hollow sleeve 184 by two annular inserts 188. Of course, itwill be apparent to those of skill in the art that in some circumstancesradiation sources assemblies 176 will not require a sleeve and radiationsource 180 may be placed directly in the fluid to be treated.

Each sleeve 184 is closed at the end distal support leg 160 and ishermetically joined to a mounting tube 192 connected to support leg 160.The hermetic seal between sleeve 184 and mounting tube 192 isaccomplished by inserting the open end of sleeve 184 into a mount 196which is hermetically fastened to the end of mounting tube 192. A rubberwasher-type stopper 200 is provided at the base of mount 196 to preventsleeve 184 from breaking due to it directly contacting housing 196 as itis inserted. A pair of O-ring seals 204, 208 are placed about theexterior of sleeve 184 with an annular spacer 206 between them.

After sleeve 184, O-ring seals 204, 208 and annular spacer 206 areinserted into mount 196, an annular threaded screw 212 is placed aboutthe exterior of sleeve 184 and is pressed into contact with mount 196.The threads on screw 212 engage complementary threads on the interior ofmount 196 and screw 212 is tightened to compress rubber stopper 200 andO-ring seals 204 and 208, thus providing the desired hermetic seal.

The opposite end of each mounting tube 192 is also threaded and is matedto a screw mount 216 which is in turn welded to support leg 160. Theconnections between mounting tube 192 and screw mount 216 and betweenscrew mount 216 and support leg 160 are also hermetic thus preventingthe ingress of fluid into the hollow interior of mounting tube 192 orsupport leg 160.

Each radiation source 180 is connected between a pair of electricalsupply conductors 220 which run from connector box 172 to radiationsource 180 through the inside of support leg 160 and mounting tube 192.

As best shown in FIGS. 4 and 5, a cleaning assembly 224 is also includedon each radiation source assembly 176 and mounting tube 192. Eachcleaning assembly 224 comprises a cylindrical sleeve 228 which acts as adouble-action cylinder. Cylindrical sleeve 228 includes an annular seal232, 234 at each end of the sleeve. Seal 232, which is adjacent supportleg 160, engages the exterior surface of mounting tube 192 while seal234, which is distal support leg 160, engages the exterior surface ofradiation source assemblies 176.

The exterior of mount 196 includes a groove in which an O-ring seal 236is placed. O-ring seal 236 engages the inner surface of cylindricalsleeve 228 and divides the interior of cylindrical sleeve 228 into twochambers 240 and 244. Chamber 240 is connected to conduit 248 andchamber 244 is connected to conduit 252. Each of conduits 248 and 252run from connector box 172, through the interior of support leg 160 andthrough the interior of mounting tube 192, to mount 196 where theyconnect to chambers 240 and 244, respectively.

As will be readily understood by those of skill in the art, by supplyingpressurized hydraulic oil, air or any suitable fluid to chamber 240through conduit 248, cylindrical sleeve 228 will be urged toward supportleg 160 and will force fluid out of chamber 244 and into conduit 252.Similarly, by supplying pressurized fluid to chamber 244 through conduit252, cylindrical sleeve 228 will be urged toward sleeve 184 and willforce fluid out of chamber 240 and into conduit 248.

Conduit 252 is connected to a supply of an appropriate cleaningsolution, such as an acidic solution, and conduit 248 is connected to asupply of any suitable fluid, such as air. Thus, when it is desired toclean the exterior of sleeve 184, pressurized cleaning solution issupplied to chamber 244 while fluid is removed from chamber 240.Cylindrical sleeve 228 is thus forced to an extended position distalfrom support leg 160 and, as cylindrical sleeve 228 moves to itsextended position, seal 234 sweeps loose foreign materials from sleeve184.

When the cylindrical sleeve 228 is in its extended position, thecleaning solution in chamber 244 is brought into contact with theexterior of radiation assemblies 176, which forms the interior wall ofchamber 244, and the cleaning solution chemically decomposes and/orremoves the remaining foreign materials which are fouling radiationassemblies 176. After a preselected cleaning period, fluid is forcedinto chamber 240, the pressure on the cleaning solution is removed fromchamber 244 thus forcing cylindrical sleeve 228 to a retracted positionadjacent support leg 160. As cylindrical sleeve 228 is retracted, seal234 again sweeps loosened foreign materials from the surface ofradiation assemblies 176.

As will be understood by those of skill in the art, the above-describedcleaning assembly 224 may be operated on a regular timed interval, forexample once a day or, where the quality of the fluid being treatedvaries, in response to variations in the readings obtained fromradiation sensor 152.

Each radiation source module 148 is mounted to main body 104 byhorizontal support member 164 which has a predefined cross-sectionalshape and which is received in a complementary-shaped bore 256 in mainbody 104. The predefined shape is selected to allow easy insertion ofhorizontal support member 164 into bore 256 while preventing rotation ofhorizontal support member 164 within bore 256.

As can been seen in FIGS. 3 and 4, the length of horizontal supportmember 164 is selected such that horizontal support member 164 extendsfrom support leg 160 to a greater extent than does radiation sourceassembly 176. In this manner, radiation source assembly 176 ismaintained well clear of the inlet or outlet transition regions as theradiation source module 148 is being installed. This arrangementminimizes the possibility of damage occurring to the radiation sourceassembly 176 from impacting it against other objects while installingradiation source module 148 and this is especially true if fluid isflowing through system 100. Due to the resulting required length ofhorizontal supports 164, bores 256 are horizontally staggered onopposite faces of main body 104.

When horizontal support member 164 is fully seated within bore 256,electrical power connectors 264, cleaning solution connectors 268 andfluid connectors 272 on connection box 172 are brought into engagementwith complementary connectors on an enclosure 276. The engagement ofconnectors 264 and 272 with the complementary connectors on enclosure276 also serves to maintain horizontal support member 164 within bore256. Enclosure 276 may conveniently contain ballasts to supplyelectrical power for radiation sources 180 and pumps and storage vessels(not shown) for cleaning fluid and pressurized fluid for cleaningassemblies 224.

Recent improvements in radiation source technology have now maderadiation sources of greater intensity available and devices which arefilamentless or which emit single wavelength radiation are available. Anexample of an improved radiation source is the above-mentioned HOK35-80lamp manufactured by Philips. This fourteen inch lamp has a rated outputof 200 watts per inch for a total output of 2800 watts. In comparison,prior art UV lamps employed in fluid treatment systems had rated outputsin the order of 1 watt per inch and were five feet in length.

As these greater intensity radiation sources emit more radiation, fewerradiation sources are needed to treat a given amount of fluid. As isknown to those of skill in the art, the dosage of radiation received bythe fluid is the product of the radiation intensity and the exposuretime. The intensity of the radiation varies with the square of thedistance the radiation passes through, but the exposure time varieslinearly with the fluid flow velocity. Accordingly, it is desired tomaintain the fluid to be treated as close as possible to the radiationsources. This requires either many low intensity radiation sourcesarranged within a large treatment area or fewer high intensity radiationsources arranged within a smaller treatment area. For reasons ofefficiency, minimizing expense and for mitigating the above-mentionedrequirement of accurately controlling fluid level, the latteralternative has been adopted by the present inventor as described above.Irradiation zone 144 is designed to present a closed cross-section tothe fluid flow thereby ensuring that the fluid to be treated passeswithin a predetermined maximum distance of a minimum number of highintensity radiation sources 180. The flow rate of fluid throughirradiation zone 144 can be increased so that an acceptable rate offluid treatment is maintained with a minimum number of high intensityradiation sources.

Thus, the present system has been designed to minimize the size ofirradiation zone 144 while elevating the fluid flow velocity to obtainthe desired rate of treatment. Thus, the flow rate through irradiationzone 144 is higher than in prior art treatment devices which aretypically designed to operate at flow rates of 2 feet per second orless. In contrast, the present system may be operated at a flow ratethrough irradiation zone 144 of up to 12 feet per second.

As is known to those of skill in the art, pressure head losses through afluid conduit are a function of the square of the fluid flow velocity.Thus, high flow velocities result in increased head loss and may resultin unacceptable fluctuations in the fluid level in the treatment system.Accordingly, the present system may be provided with inlets and outletshaving large cross-sections to minimize head losses and to facilitateinsertion and removal of radiation source modules as will be discussedbelow. The actual irradiation zone 144 is a relatively short length ofreduced cross-section and is connected to the inlets and outlets byrespective transition regions. In this manner, a desired relatively highflow rate through the irradiation zone 144 may be accomplished andhydraulic head losses minimized.

Other advantages provided by the present invention include simplifiedmaintenance, as the radiation source assemblies may be cleaned offouling materials in situ, and relatively easy removal of radiationsource modules for maintenance or radiation source replacement. Further,the capability of in situ cleaning minimizes or eliminates therequirement for otherwise redundant radiation sources to be provided toreplace those removed for cleaning and it is contemplated that theelevated velocity of the fluid through the irradiation zone will reducethe amount of fouling materials which adhere to the radiation sources.

Another embodiment of a radiation source module 148B and a cleaningassembly 300 is shown in FIGS. 6 and 7 wherein like components of theprevious embodiment are identified with like reference numerals. As mostclearly shown in FIG. 7, sleeve 184 is hermetically sealed to mountingtube 192 at housing 196 in a manner very similar to the embodiment shownin FIG. 5. However, in this embodiment cleaning assembly 300 comprises aweb 304 of cleaning rings 308 and a pair of double-action cylinders312,314. Each cleaning ring 308 includes an annular chamber 316 adjacentthe surface of sleeve 184 and cleaning rings 308 are swept over sleeves184 by the movement of cylinders 312,314 between retracted and extendedpositions.

As with the embodiment shown in FIG. 4, conduits 320 and 324 run fromconnector box 172 (not shown,) through support leg 160 to cylinders 312and 314 respectively. When fluid is supplied under pressure throughconduit 320 to cylinder 312, the cylinder's piston rod 328 is forced outto its extended position. As will be understood by those of skill in theart, as piston rod 328 is extended by the supply of fluid to the chamber332 on one side of the piston 336, fluid is forced out of the chamber340 on the second side of the piston 336 and passes through connectorlink 344 to chamber 348 of cylinder 314 forcing its piston rod 328 toalso extend and the fluid in chamber 352 to be forced into conduit 324.

In order to ensure that piston rods 328 travel synchronously, cylinders312 and 314 are designed such that the volume of fluid displaced perunit of stroke of piston 336 in cylinder 312 is equal to the volume offluid received per unit of stroke of piston 336 in cylinder 314. As willbe understood by those of skill in the art, this is accomplished byselecting appropriate diameters for each of the two cylinders. As willbe further understood by those of skill in the art, a compensator valve356 is employed at the end of the extended stroke of the pistons 336 tofurther compensate for the any difference in the total volume of fluidwhich may result between chambers 332 and 352 and between chambers 348and 340.

In a similar fashion, to retract piston rods 328, pressurized fluid issupplied to conduit 324 and a second compensator valve 356 is employedto compensate for the any difference in the total volume of fluid whichmay result between chambers 332 and 352 and between chambers 348 and 340at the end of the retraction stroke.

It is contemplated that annular chambers 316 will be filled with apredetermined quantity of suitable cleaning fluid which could be changedat appropriate maintenance intervals, such as when servicing theradiation sources. Alternatively, annular chambers 316 could be suppliedwith cleaning solution via conduits run through the hollow center ofpiston rods 328.

Another preferred embodiment of the present invention is shown in FIG.8. In this embodiment a treatment system 400 includes a main body 404with a lower surface which, with base wall 406, defines a treatment zone408. Treatment zone 408 comprises an inlet transition region 412, afirst irradiation zone 416, an intermediate zone 420, a secondirradiation zone 424 and a tapered outlet zone 426. As is apparent fromthe Figure, outlet zone 426 is lower than inlet zone 412 to provide someadditional hydraulic head to the fluid being treated to offset that lostas the fluid flows through the treatment system. It will be apparent tothose of skill in the art that, in this configuration, the requirementfor level controlling gates and the like is removed as the treatmentzone 408 also performs this function through the positioning of itsinlet and outlet.

Main body 404 also includes bores 430 to receive vertical supportmembers 434 of radiation source modules 438. Radiation source modules438 are similar to the above described radiation source modules 148 butare configured for vertical positioning of the radiation sourceassemblies 442. Radiation source assemblies 442 include sleeves 446which are connected to mount stubs 450. Of course, as mentioned above,it will be understood that in some circumstances the radiation sourceassemblies 442 will not require a sleeve and may instead be placeddirectly in the fluid to be treated.

As mount stubs 450 are located above the maximum level of fluid intreatment system 400, the connection to sleeves 446 need not behermetically sealed and may be accomplished in any convenient fashion.Of course, as the connection point between sleeves and mount stubs 450is above the level of fluid within the system, the interior of sleeves446 will not be exposed to fluid.

Mount stubs 450 are in turn connected to support arms 454 which areattached to vertical support members 434. Radiation sources 458 arelocated within sleeves 446 and are connected between electrical supplylines (not shown) which are run from connectors 462, through hollowsupport arms 454 and mount stubs 450 and into sleeve 446. Connectors 462connect with complementary connectors on enclosure 466 which may includea suitable power supply and/or control means for proper operation of theradiation sources 180 and cleaning supply systems, if installed.

In this embodiment, service of radiation source modules 438 isaccomplished by lifting the radiation source modules 438 vertically toremove them from the fluid flow. While not illustrated in FIG. 8, it iscontemplated that in some circumstances the cleaning assembliesdescribed above will be desired and it will be apparent to those ofskill in the art that either of the cleaning assembly embodimentsdescribed herein, or their equivalents, can be favourably employed withthis embodiment of the present invention. Alternatively, it iscontemplated that when the sleeves 446 require cleaning, a radiationsource module may simply be removed by lifting it vertically.

As described above, fluid treatment systems typically include aradiation sensor 152 to monitor the intensity of radiation within anirradiation zone. These sensors include a radiation transmissive windowbehind which the sensor proper is mounted and the window is insertedinto the fluid flow. Of course, as with radiation source assemblies 176(442), this window becomes fouled over time.

FIG. 9 illustrates radiation sensor assembly 500 in accordance withanother aspect of the present invention. Sensor assembly 500 includes acylindrical body 502 in which a bore 504 is formed. A radiation sensorelement 508 is located at the interior wall of bore 504 adjacent to arod 512 which is radiation transmissive and which extends from a frontface plate 514 attached to body 502. Sensor element 508 is hermeticallysealed from fluid by O-rings 516 which are adjacent sensor element 508and by O-ring 520 which surrounds rod 512 at the connection pointbetween front face plate 514 and body 502. The electrical leads 524 fromsensor element 508 exit the rear of body 502 through bore 528.

Since the exposed end of rod 512 will become fouled over time, faceplate 514 also includes a cleaning jet 532. Cleaning jet 532 ishermetically connected to bore 536 with O-ring 538, through body 502,which is in turn connected to a supply of pressurized cleaning fluid(not shown) such as an acidic solution, water or air.

When pressurized cleaning fluid is pumped applied to bore 536, cleaningjet 532 directs the cleaning fluid onto the exposed surfaces of rod 512to remove fouling materials. To prevent damage to cleaning jet 532, rod512 and to streamline fluid flow, a shroud is also provided.

Radiation sensor assembly 500 may be mounted in a sleeve connected tothe treatment zone of a fluid treatment system as will be apparent tothose of skill in the art. Radiation sensor assembly 500 can bemaintained within such a sleeve by a set screw (not shown) which isreceived in keyway 540. Of course, as is known by those of skill in theart, for accurate results it is desired that rod 512 be orientatedsubstantially perpendicular to the radiation sources 180 beingmonitored.

It is contemplated that in normal use, radiation sensor assembly 500will be cleaned by supplying a predetermined amount of cleaning solutionor water at predefined time intervals, to cleaning jet 532.

It should be understood that, while exemplary embodiments of the presentinvention have been described herein, the present invention is notlimited to these exemplary embodiments and that variations and otheralternatives may occur to those of skill in the art without departingfrom the intended scope of the invention as defined by the attachedclaims.

What is claimed is:
 1. A gravity fed fluid treatment system comprising:afluid inlet; a fluid outlet; an irradiation zone disposed between thefluid inlet and fluid outlet, the irradiation zone (i) including atleast one radiation source and, (ii) having a closed cross-section toconfine fluid to be treated within a predefined maximum distance fromthe at least one radiation source; cleaning means to remove undesiredmaterials from an exterior of said at least one radiation source, saidcleaning means comprising a cleaning sleeve surrounding said at leastone radiation source, said cleaning sleeve being movable between aretracted position wherein a first portion of said at least oneradiation source is exposed to a fluid flow and an extended positionwherein said first portion of said at least one radiation source iscovered by said cleaning sleeve, said cleaning sleeve including achamber surrounding and in contact with the exterior of said at leastone radiation source, said chamber being supplied with a cleaningsolution suitable to remove undesired materials from the exterior ofsaid at least one radiation source.
 2. A fluid treatment systemaccording to claim 1 wherein said at least one radiation source iselongate and has a longitudinal axis substantially parallel to thedirection of the fluid flow through said irradiation zone.
 3. A fluidtreatment system according to claim 2 wherein the cross-sectional areaof said irradiation zone is less than the cross-sectional areas of saidfluid inlet and said fluid outlet, said irradiation zone being disposedin a treatment zone including first and second transition regions, saidfirst transition region connecting said fluid inlet to said irradiationzone and said second transition region connecting said irradiation zoneto said fluid outlet, said first and second transition regions reducingpressure loss in said fluid between said fluid inlet and saidirradiation zone and between said irradiation zone and said fluidoutlet, respectively.
 4. A fluid treatment system according to claim 3wherein said at least one radiation source comprises at least oneultraviolet lamp and a support therefor.
 5. A fluid treatment systemaccording to claim 4 wherein said radiation source includes a sleeveabout a portion of the exterior of each of said at least one ultravioletlamp.
 6. A fluid treatment system according to claim 4 wherein saidlongitudinal axis is substantially horizontal.
 7. A fluid treatmentsystem according to claim 3 wherein said longitudinal axis issubstantially vertical and said first transition region alters asubstantially horizontal fluid flow through said fluid inlet to asubstantially vertical fluid flow through said irradiation zone.
 8. Afluid treatment system according to claim 7 wherein said secondtransition region alters said substantially vertical fluid flow throughsaid first irradiation zone to a substantially horizontal fluid flowthrough said fluid outlet.
 9. A fluid treatment system according toclaim 3 including a first radiation source located upstream of andextending into said irradiation zone and a second radiation sourcelocated downstream of and extending into said irradiation zone.
 10. Afluid treatment system according to claim 1 wherein the cross-sectionalarea of said irradiation zone is less than at least one of thecross-sectional area of said fluid inlet and the cross-sectional area ofsaid fluid outlet.
 11. A fluid treatment system according to claim 10wherein the cross-sectional area of said irradiation zone is less thanthe cross-sectional area of the fluid inlet and said irradiation zone isdisposed in a treatment zone including a transition region connectingsaid fluid inlet to said irradiation zone, said transition regionreducing pressure loss in said fluid between said inlet and saidirradiation zone.
 12. A fluid treatment system according to claim 10wherein the cross-sectional area of said irradiation zone is less thanthe cross-sectional area of the fluid outlet and said irradiation zoneis disposed in a treatment zone including a transition region connectingsaid fluid outlet to said irradiation zone, said transition regionreducing pressure loss in said fluid between said outlet and saidirradiation zone.
 13. A fluid treatment system according to claim 1wherein said cleaning sleeve includes a seal between the exteriorsurface of said at least one radiation source and said cleaning sleeve,said seal removing a portion of said undesired materials from theexterior of said at least one radiation source when said cleaning sleeveis moved between said retracted and extended positions.
 14. A fluidtreatment system according to claim 1 wherein said supply of saidcleaning solution is pressurized to said cleaning sleeve and saidcleaning sleeve is extended to said extended position by said pressure.15. A fluid treatment system according to claim 14 wherein said cleaningsleeve is retracted to said retracted position by the removal of saidpressurized cleaning solution from said cleaning sleeve.
 16. A radiationsource module for use in a fluid treatment system, comprising:a firstsupport member; at least one radiation source extending from said firstsupport member; a second support member extending from said firstsupport member, wherein said at least one radiation source extends fromsaid first support member substantially parallel to said second supportmember, said second support member extending from said first supportmember and having a free end; and cleaning means to remove undesiredmaterials from an exterior of said at least one radiation source, saidcleaning means comprising a cleaning sleeve surrounding said at leastone radiation source, said cleaning sleeve being movable between aretracted position wherein a first portion of said at least oneradiation source is exposed to a fluid flow and an extended positionwherein said first portion of said at least one radiation source iscovered by said cleaning sleeve, said cleaning sleeve including achamber surrounding and in contact with the exterior of said at leastone radiation source, said chamber being supplied with a cleaningsolution suitable to remove undesired materials from the exterior ofsaid at least one radiation source.
 17. A radiation source moduleaccording to claim 16 wherein said second support member extends fromsaid first support member to a greater extent than said at least oneirradiation source.
 18. A radiation source module according to claim 17wherein said radiation source further comprises a sleeve about saidultraviolet lamp to provide an insulating gap between said ultravioletlamp and said fluid.
 19. A radiation source module according to claim 16wherein said at least one radiation source comprises an ultravioletlamp.
 20. A radiation source module according to claim 19 wherein atleast two of said ultraviolet lamps are connected to each first supportmember.
 21. A radiation source module according to claim 16 wherein saidfirst support member includes conduit means through which an electricalpower supply is provided to said radiation source.
 22. A cleaningapparatus for a radiation source assembly in a fluid treatment system,comprising:a cleaning sleeve engaging a portion of the exterior saidradiation source assembly and movable between a retracted positionwherein a first portion of said radiation source is exposed to a flow offluid to be treated and an extended position wherein said first portionof said radiation source assembly is covered by said cleaning sleeve,said cleaning sleeve including a chamber in contact with said firstportion of said radiation source assembly and being supplied with acleaning solution suitable to remove undesired materials from said firstportion.
 23. A cleaning apparatus according to claim 22 furthercomprising at least one seal between the exterior surface of saidradiation source assembly and said cleaning sleeve, said at least oneseal removing a portion of said undesired materials from the exterior ofsaid radiation source assembly when said cleaning sleeve is movedbetween said retracted and extended positions.
 24. A cleaning apparatusaccording to claim 23 wherein said cleaning sleeve is retracted to saidretracted position by the removal of said pressurized cleaning solutionfrom said cleaning sleeve.
 25. A cleaning apparatus according to claim22 wherein said supply of said cleaning solution is pressurized to saidcleaning sleeve and said cleaning sleeve is extended to said extendedposition by said pressure.
 26. A cleaning apparatus according to claim22 wherein said cleaning sleeve engages a portion the exterior of atleast two radiation source assemblies.
 27. A cleaning apparatusaccording to claim 26 wherein said cleaning sleeve is connected to atleast one means to move said cleaning sleeve between said retracted andextended positions.
 28. A cleaning apparatus according to claim 27wherein said at least one means to move is hydraulically operated.
 29. Acleaning apparatus according to claim 27 wherein said at least one meansto move is pneumatically operated.
 30. A method of treating a fluidcomprising the steps of:(i) providing a gravity fed flow of fluid to afluid inlet; (ii) feeding the flow of fluid from the fluid inlet to anirradiation zone comprising at least one radiation source and having aclosed cross-section; (iii) confining the flow of fluid within apredefined maximum distance from the at least one radiation source; (iv)exposing the flow of fluid to radiation from the radiation source; (v)feeding the flow of fluid from step (iv) to a fluid outlet; and (vi)cleaning undesired materials from an exterior of the radiation source,said cleaning step including the steps of providing a cleaning sleevesurrounding the radiation source, moving the cleaning sleeve between aretracted position wherein a first portion of the radiation source isexposed to the fluid flow and an extended position wherein the firstportion of the radiation source is covered by the cleaning sleeve, andproviding in the cleaning sleeve a chamber which surrounds and is incontact with the exterior of the radiation source, the chamber beingsupplied with a cleaning solution suitable to remove undesired materialsfrom the exterior of the radiation source.
 31. A method according toclaim 30 wherein the flow of fluid is at a first velocity in said fluidinlet, a second velocity in said irradiation zone and a third velocityin said fluid outlet.
 32. A method according to claim 31 wherein saidsecond velocity is greater than at least one of said first velocity andsaid third velocity.
 33. A method according to claim 31 wherein saidsecond velocity is greater than both of said first velocity and saidthird velocity.
 34. A method according to claim 33 wherein said thirdvelocity is substantially equal to said first velocity.
 35. A methodaccording to claim 33 wherein prior to step (ii), the fluid flow isadmitted to a transition zone which increases the velocity thereof. 36.A method according to claim 33 wherein prior to step (v) , the fluidflow is admitted to a transition zone which decreases the velocitythereof.
 37. A method of removing fouling materials from a radiationsource in situ in a fluid treatment system, comprising the steps of:(i)providing a supply of a cleaning fluid to a cleaning chamber which iscoupled to a cleaning sleeve surrounding the radiation source, saidcleaning solution being suitable to remove undesired materials from anexterior of the radiation source; (ii) moving said chamber to surroundand be in contact with the exterior of said radiation source for apredetermined time period, said cleaning chamber maintaining saidcleaning fluid in contact with said exterior; (iii) removing saidcleaning chamber from contact with said exterior of said radiationsource after said predetermined time period.
 38. A method according toclaim 37 wherein said cleaning chamber includes a seal member inslidable engagement with said exterior and sweeping said exterior tofurther remove fouling materials when said cleaning chamber is movedinto and out of contact with said exterior.
 39. A method according toclaim 37 wherein said cleaning chamber simultaneously contacts a likeexterior of at least two radiation sources.